Along-track and gridded altimetric observations of sea level are colocated and combined with data from drifter observations and wind reanalysis to reconstruct global instantaneous near-surface horizontal momentum balance. This reconstruction includes not only geostrophic terms, but also Lagrangian accelerative terms and turbulent stress terms. The methodology developed quantifies the degree of closure, distinguishes balanced signals from errors, and estimates dynamical compensation between pairs of terms. Overall, the residual variance of the momentum balance is about 20% of the sum of individual terms variance. We carry out a detailed exploration of the misclosure, which is dominated by unbalanced signals in drifter observations (resolution mismatch accounts for 41% of the total error), followed by instrumental and spatial colocation errors. Although geostrophy is the leading order equilibrium, ageostrophic contributions associated with non-linear balanced motions, internal tides and near-inertial waves account for one third of the global balanced signal variance.  Momentum balance reconstructions and the methodology developed here for that purpose hold promise for validating SWOT sea level observations, for quantifying our ability to estimate the ocean circulation from these observations, and for improving our understanding of ocean near-surface dynamics.